The present invention relates to a retractor in which a seat belt is wound so that it can be drawn out, and more particularly to a retractor equipped with a webbing guide located adjacent to a bobbin for winding a seat belt to define a belt moving path.
Conventionally, retractors (winding devices) have been used to retract or wind seat belts for holding occupants in a vehicle safely to seats, and are constructed as shown in e.g. FIG. 17.
The retractor as shown is a retractor equipped with a clamping mechanism disclosed in e.g. U.S. Pat. No. 5,137,226. The retractor is composed of a retractor base 3 made from a metal plate having a pair of opposite side walls 1 and a rear plate 2 (bottom plate) connecting them to each other and attached to a fixed structure (e.g. car body), a bobbin 5 around which a webbing 4 is wound which is rotatably supported by both side walls 1 so as to serve as a seat belt, a webbing guide 6 fixed to a retractor base 3 so that the webbing 4 is drawn out from a predetermined position on the retractor base 3, and a clamping mechanism 7 which clamps the webbing 4 positioned at the predetermined position by the webbing guide 6 so as to inhibit the drawing out of the webbing 4.
Incidentally, the end of the webbing is formed to have a loop portion 10 capable of receiving a shaft member. On the other hand, the bobbin 5 is fixed to a winding shaft 11 which penetrates through its central portion, and is rotatably supported by the pair of side walls 1 of the retractor base 3. The bobbin rotates integrally with the winding shaft 11. Further, the bobbin 5 has a slit-like opening 12 into which the loop portion 10 of the webbing 14 is inserted. The end of the webbing 4 is fixed to the bobbin 5 so that the shaft member 13 fixed to the bobbin 5 is received in the loop portion 10 inserted into the bobbin 5 from the opening 12.
Although not shown, usually, on one side of the winding shaft 11 rotatably supported to the retractor base 3, a winding spring device is arranged to bias the bobbin 5 in a webbing winding direction. On the other side of the winding shaft 11, an emergency locking mechanism is provided to detect the occurrence of an emergency from a speed change due to an abrupt braking operation or collision so that a locking hook is locked with a hook wheel integral to the winding shaft 11 or bobbin 5, thereby inhibiting the rotation of the bobbin 5 in a webbing drawing out direction.
The webbing guide 6 defines or regulates the position of the webbing 4 so that the webbing 4 goes in and out at a predetermined position on the retractor base 3 when the webbing 4 wound around the bobbin 5 is drawn out or wound. In the case of this example,as also shown in FIG. 18, the webbing guide is fixed to the retractor base 3 in the neighborhood of the bobbin 4 and has a structure composed of a first positioning portion 14 and a second positioning portion 15. The respective positioning portions 14 and 15, as seen from FIG. 17, have the corresponding through-holes 18 and 19 for inserting the webbing 14. The peripheral wall of each of the through-holes 18 and 19 of the positioning portions 14 and 15 abuts on the surface of the webbing 4 to regulate the position of the webbing 4 so that the webbing 4 moves while it is parallel to the rear plate 2 of the retractor base 3.
As described above, upon occurrence of an emergency such as abrupt braking or collision, the emergency locking mechanism operates to inhibit the rotation of the bobbin 5 towards the webbing draw-out direction. But, generally, in the bobbin 5, an excess winding amount of the webbing 4 is so set that a suitable length of the webbing 4 remains on the bobbin 5 even when a seat belt is being used. For this reason, even when the emergency locking mechanism operates, the tension acting on the webbing 4 tightens the winding of the webbing 4 remaining on the bobbin 5 so that a length of the webbing 4 is drawn out due to tightening in the webbing wound on bobbin 5. As a result, the restriction of the occupants may be attenuated.
The clamping mechanism 7 serves to inhibit the drawing out of the webbing 4 due to the tightening of the webbing 4 remaining on the bobbin 5. In the illustrated example, the clamping mechanism 7 inhibits the drawing out of the webbing 4 in such a way that the webbing 4 is held by a pair of locking plates 23 and 24 each having a wavy surface abutting the webbing 4 between the positioning portions 14 and 15.
The locking plate 23 arranged between the webbing 4 and the rear plate 2 of the retractor base 3, as seen from FIG. 18, is held on e.g., a saucer-like holder 26 which is supported vertically slidably along the rear plate 2 by a pair of side plate portions 16 of the webbing guide 6. The holder 26 is forced downward by a spring 27 located between the upper end of the holder 26 and the lower end of the second positioning portion 15. On the other hand, the locking plate 24, as seen from FIG. 17, is held on the end of an arm 29 which can swing on a shaft 28 hung between a pair of side walls 1 of the retractor base 3. In this case, the arm 29 serves to operate in linkage with the emergency locking mechanism (not shown). In an emergency state when the emergency locking mechanism inhibits the rotation of the bobbin 5 in the webbing draw-out direction, the arm 29 swings in the direction of an arrow a to push the locking plate 24 on the webbing and locking plate 23. Thus, the pair of locking plates 23 and 24 hold the webbing 4 to inhibit its drawing out motion.
The conventional retractor as shown in FIG. 17 has been installed for use in such a manner that the direction of drawing out the webbing 4 from the retractor base 3 is in parallel to the rear plate 2 of the retractor base 3. For example, the upper end surface in which the inserting through-hole 19 of the second positioning portion 15 forms a flat surface orthogonal to the inserting-through direction of the through-hole 19.
However, the direction of drawing out the webbing 4 from the retractor base 3 is decided depending on many conditions such as the manner of drawing out the webbing in use (draw-out path), the shape of a fixed structure (e.g. car body) to which the retractor base 3 is attached, etc. Therefore, actually, it is not easy to install the retractor 4 so that the direction of drawing out the webbing 4 from the retractor base 3 is in parallel to the rear plate 2 of the retractor base 3. For example, where common retractors are installed in vehicles having different body shapes, attachment metal fittings for position regulating to be arranged between the body and retractor base 3 must be individually prepared for each type of vehicle. If not, like state B or state C as shown by two-dot chain lines in FIG. 17, the direction of the webbing 4 drawn out from the retractor base 3 may be greatly altered.
When the direction of drawing out the webbing 4 is greatly tilted from the defined direction, in the conventional retractor, the surface of the webbing 4 is brought into intimate contact with the upper angled portion of the inserting through-hole 19 of the second positioning portion 15 thereby to increase the contact resistance. As a result, smoothness of the draw-out and winding operations may be hindered.
The amount of the webbing 4 between the bobbin 5 and the first positioning portion 14 changes in accordance with the winding diameter of the webbing 4 on the bobbin 5. According to the conventional retractor, although the contact angle of the webbing 4 at the first positioning portion 14 changes in accordance with the winding diameter of the webbing 4 on the bobbin 5, the abutting face of the first positioning portion 14 on the webbing 4 is a simple continuous curve. Therefore, when the diameter of the webbing 4 decreases to tilt the webbing 4 greatly for the first positioning portion 14, the contact area increases to increase the contact resistance. As a result, smoothness of the drawing out and winding operations is hindered.
Further, it should be noted that the length of the webbing 4 drawn out from the retractor base 3 when a seat belt is being used depends on the size of a seat, the occupant's body shape, the position where the retractor base 3 on the body is attached, etc. Therefore, in order to increase general versatility so that one kind of retractor can be applied to plural vehicle types, the maximum winding capacity of the webbing 4 on the bobbin 5 must be increased. Thus, even if the winding diameter of the webbing 4 changes greatly, the contact resistance between the first positioning portion 14 and the webbing 4 should not change.
But, in the conventional first positioning portion 14 as shown in FIG. 17, the continuous simple curve is provided on only the side of the bobbin 5 to abut on the surface of the webbing 4. Thus, when the winding diameter of the webbing 4 on the bobbin 5 is set at so large a value that the webbing path deviates to the side of the rear plate 2, the contact resistance increases at the angled portion of the first positioning portion 14 on the side of the rear plate 2. Therefore, it is difficult to increase the maximum winding capacity of the webbing 4 in order to increase the general versatility of the device.